1. Field of the Invention
This invention relates generally to visual display technology. More particularly, it relates to display technology for eye mounted display, and specifically to contact lens displays.
2. Description of the Related Art
More and more our technological society relies on visual display technology for work, home, and on-the-go use: document and productivity applications, text messages, email, internet access, voice calls, games, HDTV, video on demand, still and video cameras, etc. These services are delivered over different devices that mainly vary in size, for example, smartphones, dedicated digital cameras, dedicated portable game devices, tablets, laptops, desktops, TV sets, game consoles, and servers (including the cloud). What these all (but the last) have in common is a dedicated display, mainly constrained by the physical size of the particular device. Restrictions in size limit the possible field of view, which limits not just the resolution but scale of information and context available. Larger physical display sizes alleviate such limits, but rule out portability, and increases power requirements as well as cost. While there is some convergence in devices, e.g. smartphones are commonly used instead of dedicated small digital cameras, physical display size currently limits how far such convergence can go. For example, the electronics of a modern smartphone, tablet, and low power laptop are effectively identical, except for the physical display device and the incremental additional physical battery size required to power it. Thus there is a need for improvements in display technologies with respect to spatial resolution, quality, field of view, portability (both size and power consumption), cost, etc.
However, the current crop of display technologies makes a number of tradeoffs between these goals in order to satisfy a particular market segment. For example, direct view color CRTs do not allow direct addressing of individual pixels. Instead, a Gaussian spread out over several phosphor dots (pixels) both vertically and horizontally (depending on spot size) results. Direct view LCD panels have generally replaced CRTs in most computer display and TV display markets, but at the trade-offs of temporal lag in sequences of images, lower color quality, lower contrast, and limitations on viewing angles. Display devices with resolutions higher than the 1920×1024 HDTV standards are now available, but at substantially higher cost. The same is true for displays with higher dynamic range or high frame rates. Projection display devices can now produce large, bright images, but at substantial costs in lamps and power consumption. Displays for cell phones, tablets, handheld games, small still and video cameras, etc., must currently seriously compromise resolution and field of view. Within the specialized market where head mounted displays are used, there are still serious limitations in resolution, field of view, undo warping distortion of images, weight, portability, cosmetic acceptability, and cost.
The existing technologies for providing direct view visual displays include CRTs, LCDs, OLEDs, OLED on silicon, LEDs, plasma, SEDs, liquid paper, etc. The existing technologies for providing front or rear projection visual displays include CRTs, LCDs, DLP™, LCOS, linear MEMs devices, scanning laser, etc. All these approaches have much higher costs when higher light output is desired, as is necessary when larger display surfaces are desired, when wider useable viewing angles are desired, for stereo display support, etc.
Another general problem with current direct view display technology is that they are all inherently limited in the perceivable resolution and field of view that they can provide when embedded in small portable electronics products. Only in laptop computers (which are quite bulky compared to cell phones, tablets, hand held game systems, or small still and/or video cameras) can one obtain higher resolution and field of view in exchange for size, weight, cost, battery weight and life time between charges. Larger, higher resolution direct view displays are bulky enough that they must remain in the same physical location day to day (e.g., large plasma, LCD, or OLED display devices).
One problem with current rear projection display technologies is that they tend to come in very heavy bulky cases to hold folding mirrors. And to compromise on power requirement and lamp cost most use display screen technology that preferentially passes most of the light over a narrow range of viewing angles.
One problem with current front projection display technology is that they take time to set up, usually need a large external screen, and while some are small enough to be considered portable, the weight savings comes at the price of color quality, resolution, and maximum brightness. Many also have substantial noise generated by their cooling fans.
Current head mounted display technology have limitations with respect to resolution, field of view, image linearity, weight, portability, and cost. They either make use of display devices designed for other larger markets (e.g., LCD devices for video projection), and put up with their limitations; or custom display technologies must be developed for what is still a very small market. While there have been many innovative optical designs for head mounted displays, controlling the light from the native display to the device's exit pupil can result in bulky, heavy optical designs, and rarely can see-through capabilities (for augmented reality applications, etc.) be achieved. While head mounted displays require lower display brightness than direct view or projection technologies, they still require relatively high display brightness because head mounted displays must support a large exit pupil to cover rotations of the eye, and larger stand-off requirements, for example to allow the wearing of prescription glasses under the head mounted display.
Thus, there is a need for new display technologies to overcome the resolution, field of view, power requirements, bulk and weight, lack of stereo support, frame rate limitations, image linearity, and/or cost drawbacks of present display technologies
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